The invention relates to a process for increasing the process temperature of an air compressing internal combustion engine with an exhaust gas recirculation line arranged between the exhaust gas line and an intake air line. A final control element is adjusted by a power-assisted actuator activated by a control unit. This actuator sets an amount of recirculated exhaust gas in dependence upon speed and loading of the internal combustion engine and atmospheric pressure.
It is shown in German published unexamined patent application No. 34 19 069 to determine the amount of recirculated exhaust gas with an air compressing internal combustion engine on the basis of speed and load of the internal combustion engine and also the intensity of the light fuel flame burning in the cylinder.
Furthermore, an internal combustion engine with an apparatus for preheating the combustion air is shown in German published unexamined patent application No. 26 50 946. A control of the preheated combustion air is performed as a function of the coolant temperature.
An object of the present invention is to achieve an increased process temperature in a short period, with unrestricted power output of the internal combustion engine, while taking emissions into account.
These and other objects are achieved according to the present invention by a process for increasing the process temperature of an air compressing internal combustion engine in which the process includes preheating of the intake air when the temperature of the coolant is below a first predetermined limit, and: (a) the speed of the engine is between a lower speed and an upper speed, and said engine is operating at a power level below 90% of the useful power of the engine; or (b) the engine speed is between this upper speed and a speed that corresponds to 90% of the nominal engine speed, and the engine is operating at a power level below 75% of the useful power of the engine. This process also includes recirculating exhaust gas when the coolant temperature is between the first predetermined limit and a lower, second predetermined limit and the upper and higher speed, and said engine is operating at a power level below 75% of the useful power of the engine. This recirculation is reduced when a predetermined vehicle velocity is exceeded and the engine is operating at a power level at or above 50% of the useful power of the engine.
The objects of the invention are also achieved according to another preferred embodiment of the present invention for a process for increasing the process temperature of an air compressing internal combustion engine in which a control unit sets an instantaneous amount of recirculated exhaust gas with reference to speed and load of the internal combustion engine, and also a coolant temperature and atmospheric pressure. The process includes determining a temperature value dependent on load and speed from a predetermined family of characteristic intake air temperature curves. The temperature value is corrected in dependence on coolant temperature, and then supplied as a set value to a governor which changes the influx of preheated intake air to the stream of intake air by a first final control element. Exhaust gas is mixed with the preheated stream of intake air by the operation of a second final control element which is in the exhaust gas recirculation line, the mixing being done depending upon a predetermined internal combustion engine speed. The pivot angle of a pressure control valve which is upstream of the junction of the exhaust gas recirculation line into an air circulation housing is controlled depending on load and speed from a predetermined family of characteristic pressure control valve curves. The pivot angle is corrected depending on intake air temperature, coolant temperature and atmospheric pressure. The corrected pivot angle is supplied to a pressure control valve position governor which positions the pressure control valve via an actuator. The position of the second final control element is then determined in dependence on speed and load from a family of characteristic exhaust gas recirculation curves. The final control element position is then corrected depending on the intake air temperature, coolant temperature and atmospheric pressure. The corrected final control element position is then supplied to an exhaust gas recirculation position governor.
The process according to the invention has the advantage that, by the combined use of exhaust gas recirculation and intake preheating, an increased process temperature for the purpose of regeneration of a soot burn-off filter in the exhaust system of the air compressing internal combustion engine for example, is achieved very early. Further, because of the interaction of the intake air preheating and the exhaust gas recirculation, the latter is used only to a reduced extent. Owing to a reduced amount of recirculated exhaust gas, there are also fewer sulphur-contaminated particles supplied to the combustion chamber, and thus also to the lubricating oil in which acids form. The lesser loading of the lubricating oil makes more economical oil change intervals feasible at the same time along with less wear.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.